Conventional fabrication methods for printed circuits have always utilized one or more methods of creating a conductive metal pattern on a dielectric substrate. Some of the various methods include print and etch, electroless copper deposition, vacuum deposition, and on-contact screen printing, contact printing, or ink jetting a liquid slurry of metal onto the substrate. Some of these methods are subtractive, such as the “print and etch” technique where patterns are etched from a laminated copper foil, others are purely additive, such as screen or thick film printing where conductor patterns are directly formed on the substrate, and still others are combinations of additive and subtractive. One technique that is gaining popularity is the fabrication of printed electronic circuitry using graphic arts technology, as it has the potential to produce very inexpensive circuits in very high volumes. However, current graphic arts technology is limited in the feature size that can be achieved, the current limit of resolution between two metal conductors being about 10-50 micrometers. Researchers are investigating the development of new functional inks and novel methods of graphic arts feature imaging, such as gravure cylinders, flexo plates, stencil screens, etc. to achieve finer printed feature resolution. All these printing techniques rely on optimizing the wetting characteristics between the ink and the substrate interface to create high resolution images. Generally, this requires some modification of the substrate wetting properties, typically via altering the substrate surface by corona discharge, chemical coating, or plasma treatment. Although these techniques can alter the substrate surface enough to provide good adhesion and wetting, they increase the surface roughness, thereby limiting the formation of very fine features, such as spaces between printed structures, i.e. conductors, of less than 10 micrometers. An improved method of forming fine features on printed circuitry using graphic arts techniques would be a significant contribution to the art.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.